This chapter is from the book
This chapter is from the book
This chapter is from the book
The Battle for Voice Quality
Even though IP-based communications have matured since the 1990s, many organizations and individuals are still skeptical in relying on VoIP for reasons such as dependence on power and the quality of the service compared to traditional telephony services, put simply, the analog dial tone. Since Microsoft’s entry into the Unified Communications marketplace, the question of voice quality was the primary target of Microsoft’s competitors, specifically Cisco. Telecommunication providers such as Cisco, Avaya, Nortel, and others sell Quality of Service (QoS) along with their devices and application platforms. QoS networking routers and switches provide compression on the codecs that are used to transmit the audio that initiates from one phone to the other or one PBX to the other. These existing telephony players use legacy codecs as well, which force them to use QoS devices and services to ensure that the quality of the call is clear. For example, the audio codec used for SIP calling is G.711. For more detailed information about this codec, visit the ITU Web site via http://itu.int. The PBX uses this codec at a rate of 64KB per second to transmit the audio. The telephony provider will usually provide a QoS router that keeps this compression low to make sure that disturbances such as jitter, lossless audio, and echoing do not occur during the transmission. Bottom line, telephony providers are obsessed with this feature, and for good reason, but it seems to be the only thing they are obsessed with outside of raping the customer with overpriced, unnecessary hardware.
Microsoft took a different approach to QoS by adding Quality of Experience (QoE) to the equation. To explain QoE, you need to know that all Unified Communications providers, including Microsoft, use Mean of Opinion (MOS) scores to determine the measurement of quality of the communications infrastructure. MOS can be used for video and voice as well. Table 1.1 outlines an example of a MOS score report covering many different codecs within a company’s telephony environment.
Table 1.1. MOS Scores
|
Codec |
Kilobytes/Second |
MOS Score |
|
G.711 (ISDN) |
64 |
4.3 |
|
iLBC |
15.2 |
4.14 |
|
AMR |
12.2 |
4.14 |
|
G.729 |
8 |
3.92 |
|
G.723.1r63 |
6.3 |
3.9 |
|
GSM EFR |
12.2 |
3.8 |
|
G.726 ADPCM |
32 |
3.8 |
|
G.729a |
8 |
3.7 |
|
G.723.1r53 |
5.3 |
3.65 |
|
GSM FR |
12.2 |
3.5 |
Source: http://en.wikipedia.org/wiki/Mean_opinion_score
MOS scores are rated between a range of 1 and 5 based on categories of rating in Table 1.2.
Table 1.2. MOS Score Ratings
|
MOS |
Quality |
Impairment |
|
5 |
Excellent |
Imperceptible |
|
4 |
Good |
Perceptible but not annoying |
|
3 |
Fair |
Slightly annoying |
|
2 |
Poor |
Annoying |
|
1 |
Bad |
Very annoying |
Source: http://en.wikipedia.org/wiki/Mean_opinion_score
Microsoft took this a step further by adding QoE to not only provide quality of the communications service from a networking perspective, but also from a user experience perspective. While QoS looks only at the hard evidence of the system, QoE factors in the actual user experience. This means that even though the QoS reports may be perfect, some of the users within the same reported environment may still experience static or some other kind of line trouble, so the QoS may result overall in a good score, but bottom line the service is still not operational, especially if the CEO is the user experiencing the line interference. Microsoft created its own QoE Monitoring Server that diagnoses and collects reports on the experience of each communication endpoint (see Figure 1.10). As soon as a call or session is completed, reports and statistics are sent to the server and are available for review. Metrics are taken in real time during each user session so that the true user experience is captured to ensure the quality of the overall service.
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Figure 1.10 An example of a QoE report generated from the Microsoft QoE Monitoring Server